Wastewater compounds (WWCs) are organic compounds of natural or synthetic origin typically found in domestic and industrial wastewaters. WWCs include many classes of compounds: surfactants, flame retardants, plasticizers, industrial solvents, disinfectants, domestic pesticides, pharmaceuticals, and personal-care products (Zaugg and others, 2002). These compounds and degradates survive wastewater-treatment processes and are expelled into the environment in treated wastewater (Lee and others, 2004). Recent studies of WWCs downstream from wastewater-treatment facilities in Minnesota indicated concentrations twice those observed upstream (Lee and others, 2004). Kolpin and others (2002) found WWCs in 80 percent of U.S. streams sampled, with median concentrations generally less than 1 µg/L. Mixtures of compounds were common in the samples collected, with a maximum of 38 and a median of 7 compounds detected in samples. WWCs have also been detected in drinking water (Lee and others, 2004).

A subset of WWCs analyzed for in Phase II consist of substances known to or are suspected to disrupt endocrine function in vertebrate organisms. Termed endocrine-disrupting chemicals (EDCs), these compounds are defined by the USEPA (U.S. Environmental Protection Agency, 1997) as

“. . . an exogenous agent that interferes with the synthesis, secretion, transport, binding, action, or elimination of natural hormones in the body that are responsible for the maintenance of homeostasis, reproduction, development, and (or) behavior.”

Though few causal relations have been conclusively established between EDCs and adverse effects in vertebrates under environmental conditions, effects on test organisms in controlled laboratory settings have been shown (Taylor and Harrison, 1999; Kaiser, 2000). In contrast to most toxic chemicals, effects on test organisms have been seen at very low EDC concentrations, well below concentrations typically considered “safe” (Kaiser, 2000). To date, most studies have focused on the effects of a single compound; toxic effects of chemical mixtures are not known (Sullivan and others, 2005). It is thought that long-term, continual exposure to EDCs may have subtle effects on vertebrate populations over time through adverse effects on reproduction (Daughton and Ternes, 1999).

As part of Phase II, samples were collected and analyzed for WWCs, which included pharmaceuticals and personal-care products. WWC samples were collected during each sampling event, resulting in 12 samples per site.

Detection Frequencies

As mentioned in the Quality Assurance and Quality Control section, WWC data contain estimated concentrations, concentrations above the reporting level, qualitatively detected results (constituent detected but not quantified), and concentrations less than detection (table 18). Only 3 percent of stream-sample data and 1 percent of harbor-sample data reported had concentrations above the reporting level, and therefore little quantitative analysis could be performed. Results were grouped as detections/nondetections, where detections of WWCs consisted of estimated concentrations and concentrations above the reporting level.

Table 18. Summary of detections and nondetections of wastewater compounds at all Phase II sites in the Milwaukee Metropolitan Sewerage District planning area, Wis.

[All values in percent]

A total of 62 WWCs were sampled for and were aggregated into classes for the purpose of analysis (tables 19 and 20). The 15 classes of WWCs were based on aggregations by Sullivan and others (2005), appendix 4-3, p. 353. WWC classes were organized into four groups in an effort to identify sources of WWC contribution to stream and harbor sites (table 19). At the site level, these groupings aided in the understanding of the persistence of WWC classes as they moved from stream sites to harbor sites, distribution of WWC classes, and relations between WWC classes. The 15 classes aided in the understanding of WWC response to flow, seasonality, and the combined effects of flow and seasonality. These groups were also used to organize information regarding the individual constituents driving detections and (or) responses in each class.

Table 19. Grouping of wastewater-compound (WWC) classes for Phase II of the Milwaukee Metropolitan Sewerage District Corridor Study.

[PAH, polycyclic aromatic hydrocarbon]

Table 20. Summary of analytical results of stream and harbor sites sampled for wastewater compounds (WWCs) during Phase II of the Milwaukee Metropolitan Sewerage District Corridor Study.

[CAS, Chemical Abstracts Service; µg/L, microgram per liter; DF, detection frequency; ND, not detected; e, estimated; %, percent; >, greater than; UV, ultraviolet; PAH, polycyclic aromatic hydrocarbon; bold compound names indicate known or suspected endocrine distruptors]

  ¹ Determined from only those samples with detections.
  ² Zaugg and others, 2002; Lee and others, 2004

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Of the 62 constituents sampled for during Phase II, 50 were detected in at least one sample collected from the stream or harbor. The 12 constituents not detected in any sample vary in WWC class and indicated no particular pattern (table 20). Forty-nine constituents were detected in at least one stream sample. The only constituent not detected in streams that was detected in harbor samples was chlorpyrifos, an insecticide. Harbor samples had fewer constituent detections overall, with only 34 constituents detected in one or more samples. The constituents not detected in the harbor samples (table 20) also varied in WWC class; in some cases, there were no detections for an entire WWC class in harbor samples. The two WWC classes not detected in harbor samples were antimicrobial disinfectants and antioxidants. Overall, 93 percent (217 of 234) of both stream and harbor samples contained a minimum of one WWC detection. At stream sites, the number of constituents detected in samples ranged from 1 to 29, with more than half the samples containing nine or more WWCs. In harbor samples, the number of constituents in samples ranged from 1 to 22, with over half the samples containing two or more WWCs.

In streams, the most frequently detected class of constituents was herbicides (greater than 90 percent DF), followed by nonprescription human drugs (greater than 80 percent DF) (figs. 44–47). In harbor samples, the most frequently detected class of constituents was flavors and fragrances (greater than 60 percent DF), closely followed by insecticides and solvents.

Figure 44. Detection frequencies of selected classes of Group 1 wastewater compounds (WWCs) (polycyclic aromatic hydrocarbons (PAHs), antioxidants, plasticizers, dyes and pigments, and fire retardants), by site, in the Milwaukee Metropolitan Sewerage District planning area, Wis. Site abbreviations listed in table 1.

Figure 45. Detection frequencies of Group 2 solvent and fuel wastewater-compound (WWC) classes, by site, in the Milwaukee Metropolitan Sewerage District planning area, Wis. Site abbreviations listed in table 1.

Figure 46. Detection frequencies of Group 3 insecticide and herbicide wastewater-compound (WWC) classes, by site, in the Milwaukee Metropolitan Sewerage District planning area, Wis. Site abbreviations listed in table 1.

Figure 47. Detection frequencies of selected classes of Group 4 wastewater compounds (WWCs) (flavors and fragrances, nonprescription human drugs, antimicrobial disinfectants, detergent metabolites, and sterols), by site, in the Milwaukee Metropolitan Sewerage District planning area, Wis. Site abbreviations listed in table 1.

The sites where several classes of WWCs were detected frequently were Lincoln Creek, Milwaukee River at Mouth, Little Menomonee River, Underwood Creek, and Honey Creek). Of these sites, Kinnickinnic River had the highest detection frequency in the most classes (5 of the 15 WWC classes). No consistent response was observed between any WWC class and land use.

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Response to Flow and Seasonality

At the stream sites, WWC classes did not show a consistent response with respect to flow alone (table 21, fig. 48). A seasonal response was more apparent (fig. 49); when flow and seasonality was considered together (figs. 50 and 51, table 21), certain groups indicated more consistent responses. In the following discussions of the effects of combined flow and seasonality on stream samples, autumn samples were not discussed because there was a lack of high-flow-event samples collected during that season.

Table 21. Detection frequencies for Phase II wastewater compounds (WWC) analysis in the Milwaukee Metropolitan Sewerage District planning area, Wis.

[All detection frequencies given in percent; PAH, polycyclic aromatic hydrocarbon]

Figure 48. Detection frequency of stream samples with wastewater-compound (WWC) detections during high- and low-flow periods, by WWC class (and number of constituents), in the Milwaukee Metropolitan Sewerage District planning area, Wis.

Figure 49. Detection frequency of stream samples with wastewater-compound (WWC) detections, by season and WWC class (and number of constituents), in the Milwaukee Metropolitan Sewerage District planning area, Wis.

Figure 50. Detection frequency of stream samples with wastewater-compound (WWC) detections during low-flow periods, by season and WWC class (and number of constituents), in the Milwaukee Metropolitan Sewerage District planning area, Wis.

Figure 51. Detection frequency of stream samples with wastewater-compound (WWC) detections during high-flow periods, by season and WWC class (and number of constituents), in the Milwaukee Metropolitan Sewerage District planning area, Wis.

WWC classes from Group 1 indicated a variety of responses in DFs at stream sites with relation to flow, seasonality, and the combined effects of flow and seasonality. The antioxidant class had a higher DF during low-flow events than during high-flow events. The DF observed in winter samples was the highest of any season. When flows were combined with seasonality, the highest DF (29 percent) was observed during winter low-flow events while no detections occurred during winter high-flow events. The dyes and pigments class had a higher DF during high-flow events (77 percent) than during low-flow events (67 percent); however the difference was not very pronounced. No consistent seasonal response was observed, and no additional response was observed when flows were combined with seasonality. The fire-retardant class did not indicate consistent responses with respect to flow or season. PAHs indicated a moderate response with respect to flow, with samples collected during high-flow events having a higher DF than those collected during low-flow events (70 percent and 59 percent, respectively). Spring and winter had the highest DFs (both 77 percent) while autumn had the lowest (33 percent). No additional response was observed when flows were combined with seasonality. The plasticizer class indicated a moderate response with respect to flow, with samples collected during low-flow events (59 percent) having a higher DF than those collected during high-flow events (45 percent). Samples collected during autumn had the lowest DF (37 percent) while those collected in spring, summer, and winter all had approximately the same DFs (around 55 percent). No additional response was observed when flows were combined with seasonality.

WWC classes from Group 2 indicated a variety of responses in DFs at stream sites with relation to flow, seasonality, and the combined effects of flow and seasonality. The fuel class did not show a consistent response with respect to flow. The highest DFs of fuel occurred during winter (20 percent) and spring (15 percent). When flows were combined with seasonality, the highest DFs occurred during winter high-flow events (31 percent) and spring low-flow events (25 percent). The solvent class did not indicate a consistent response with respect to flow. Samples collected in the spring had the highest DF (23 percent) while those collected in autumn had no detections. When flows were combined with seasonality, samples collected during spring low-flow events had the highest DF (35 percent). WWC classes from Group 3 indicated a variety of responses in DFs at stream sites with relation to flow, seasonality, and the combined effects of flow and seasonality. The herbicide class did not demonstrate a consistent response with respect to flow. Spring and summer had the highest DFs of herbicides (68 and 54 percent, respectively) with no detections occurring during autumn and very few occurring during winter (DF of 3 percent). When flows were combined with seasonality, spring low-flow events had the highest DF (85 percent), followed by spring high-flow events (60 percent). All winter detections of herbicides occurred during high-flow events. Insecticides indicated no consistent response with respect to flow or season alone. However, when flows were combined with seasonality, winter low-flow events had the highest DF (100 percent). This observation was unexpected and was thought to be caused by contamination of samples by field vehicles or equipment.

WWC classes from Group 4 indicated a variety of responses in DFs at stream sites with relation to flow, seasonality, and the combined effects of flow and seasonality. The antimicrobial-disinfectant class had higher DFs during high-flow events than during low-flow events. With respect to seasonality, samples collected during winter had the highest DF (10 percent) of any season (fig. 49, table 21). The detergent metabolite class did not demonstrate a consistent response with respect to flow. With respect to seasonality, the highest DFs were observed in spring samples (38 percent). When flows were combined with seasonality, highest DFs were observed in spring and winter low-flow-event samples (50 and 43 percent, respectively). The flavors and fragrances class did not demonstrate a consistent response with respect to flow. With respect to seasonality, winter samples had the highest DF (80 percent) followed by spring (58 percent, DF); autumn had the lowest DF (23 percent). No additional response was observed when flows were combined with seasonality. The nonprescription-human-drug class did not indicate consistent responses with respect to flow or seasonality alone. When flows were combined with seasonality, winter high-flow events had the highest DF (94 percent). The sterol class did not indicate a consistent response with respect to flow. With respect to seasonality, the highest DFs occurred in winter (17 percent) and autumn samples (10 percent). When flows were combined with seasonality, no consistent response was observed with respect to seasonality. However, a consistent response was observed in relation to flow. Winter high-flow events had the highest DF (25 percent), followed by spring high-flow events (DF of 8 percent); summer high-flow-event samples had no detections for sterols (fig. 48–51, table 21). The miscellaneous class did not demonstrate a consistent response with respect to flow. With respect to seasonality, spring samples had the highest detection frequency (25 percent). When flows were combined with seasonality, spring samples collected during low-flow and high-flow events had the highest DFs (35 percent and 20 percent, respectively); no detections were observed in high-flow-event samples collected during summer or winter.

Harbor samples could only be examined for seasonal responses. Two classes of WWCs were not detected in harbor samples: antimicrobial disinfectants and antioxidants (fig. 52, table 21). The herbicide and nonprescription-human-drug classes were detected with the greatest frequency in harbor samples, with spring samples showing the highest DF at 65 percent. More classes were detected and at higher frequencies in samples collected during spring. WWCs in the fuel and miscellaneous classes were detected only in spring samples. The solvent and herbicide classes were not detected in autumn samples. The PAH and detergent metabolite classes were detected only in spring and autumn samples. The sterol class was only detected during autumn sampling (8 percent) (fig. 52, table 21).

Figure 52. Detection frequency of harbor samples with wastewater-compound (WWC) detections, by season and WWC class (and number of constituents), in the Milwaukee Metropolitan Sewerage District planning area, Wis. (No harbor samples were collected in winter.)

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Dominant Constituents in Wastewater Compound Classes

Within each class of WWCs, the data were analyzed to determine which, if any, constituent was driving detections and (or) responses for each class (table 20). DFs in stream samples were higher than those in harbor samples for every class of WWCs. Each of the classes comprising Group 1 was affected by the prevalence of detections of individual constituents within that class. Of the two constituents of the antimicrobial-disinfectant class, p-Cresol was the only constituent detected, with an overall DF of 3 percent; it was detected only in streams. It is commonly used as an industrial solvent, an insecticide, and it is an ingredient in common household cleaners and disinfectants (Agency for Toxic Substances and Disease Registry, 2006). Of the three constituents in the antioxidant class, only 5-methyl-1H-benzotriazole was detected, with an overall DF of 5 percent. It is commonly used as an antioxidant in antifreeze and deicers, and has been identified as one of the constituents found in runoff from airport deicing activities (Corsi and others, 2003). Highest DFs for this constituent were observed at the Kinnickinnic River site during a winter sampling event. The dyes and pigments class was composed of only one constituent: 9,10-anthraquinone. It had an overall DF of 57 percent, and, although it was found in both stream and harbor samples, DFs were higher in stream samples than in harbor samples. Of the three constituents in the fire-retardant class, tris(2-butoxyethyl) phosphate was the most dominant. Although all three were detected in both stream and harbor samples, tris(2-butoxyethyl) phosphate was detected most frequently, with an overall DF of 58 percent; tributyl phosphate and tris(dichloroisopropyl) phosphate both had overall DFs around 30 percent. Of the 6 constituents in the PAH class, 5 were detected in at least one sample. Fluoranthene had the highest overall DF (46 percent), followed by pyrene (37 percent) and phenanthrene (37 percent); the remaining constituents had DFs less than 30 percent in stream samples. All but one constituent in this class (anthracene) were detected in both stream and harbor samples; constituents in this class had lower DFs in harbor samples than in stream samples. Of the 3 constituents in the plasticizer class, all were detected in both stream and harbor samples, however tris(2-chloroethyl) phosphate was the dominant constituent, with an overall DF of 39 percent.

Each of the classes comprising Group 2 was affected by the prevalence of detections of individual constituents within that class. Of the 4 constituents in the fuel class, only 3 were detected in samples. The most dominant constituent was 2-Methylnaphthalene (DF of 8 percent). Both constituents in the solvent class were detected in stream and harbor samples; however, isophorone was dominant, with an overall DF of 7 percent. Isophorone is an industrial chemical used as a solvent in some printing inks, paints, lacquers, and adhesives. It is also used as an intermediate in the production of certain chemicals (Agency for Toxic Substances and Disease Registry, 1999). Tetrachloroethlyene had an overall DF of 3 percent.

Each of the classes comprising Group 3 was affected by the prevalence of detections for individual constituents within that class. Of the 5 constituents in the herbicide class, only 4 were detected in samples. Metolachlor is a pre-emergent herbicide and is commonly used to control certain broadleaf and annual grassy weeds on agricultural land and on highway rights-of-way (Oregon State University, 1996); it had the highest overall DF (39 percent), and was the WWC with the highest DF in harbor samples. Prometon is a non-selective herbicide and is commonly used for total vegetation control on industrial sites, for noncrop areas on farms, and around and under asphalt (Capel and others, 1999); it had a slightly lower overall DF (31 percent) than metolachlor. Both of these herbicides were detected in stream and harbor samples. The remaining two constituents detected (bromacil and pentachlorophenol) were detected at low frequencies in stream samples and were not detected in harbor samples. Of the six constituents in the insecticide class, DEET (the most common active ingredient in insect repellents) had the highest overall DF, at 64 percent (U.S. Environmental Protection Agency, 2005b). Carbazole was the second-most-frequently detected insecticide (overall DF of 29 percent), followed by carbaryl (overall DF of 18 percent), and diazinon (overall DF of 15 percent). Chlorpyrifos had a very low overall DF (1 percent) and was found only in harbor samples, whereas dichlorvos was detected only in stream samples, at an overall DF of less than 1 percent.

Each of the classes comprising Group 4 was affected by the prevalence of detections of individual constituents within that class. Of the 7 constituents in the detergent metabolite class, only 3 were detected in samples: diethoxynonylphenol (overall DF of 18 percent) was the most dominant constituent, followed by 4-nonylphenol (overall DF of 9 percent), and ethoxyoctylphenol (overall DF of 1 percent). Of the 10 constituents in the flavor/fragrance class, only 8 were detected in samples, the most dominant constituent being acetophenone (overall DF about 30 percent). Of the three constituents in the nonprescription-human-drug class, caffeine was the most dominant. Although all three constituents were detected in both stream and harbor samples, caffeine was the most frequently detected (overall DF of 63 percent). The remaining two constituents of this class (menthol and cotinine) were detected less frequently (26 and 35 percent overall DF, respectively). Of the four constituents in the sterol class, cholesterol was the dominant constituent, with an overall DF of 5 percent. Cholesterol is often considered as a fecal indicator, but it is also a plant sterol. All four constituents in the sterol class were detected in stream samples, but cholesterol was the only sterol detected in harbor samples. Of the 3 constituents in the miscellaneous WWC class, 1,4-dichlorobenzene was the dominant constituent, with an overall DF of 7 percent; the remaining 2 constituents had DFs of 1 and 3 percent.

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Endocrine-Disrupting Chemicals

Of the 62 WWCs, 20 are known or suspected endocrine disrupting chemicals (EDCs) (table 20, constituents in bold). Of these 20, 12 were detected and 8 were not detected. The dominant EDC constituent in all samples was tris(2-chloroethyl) phosphate (DF of 39 percent), followed by tris(dichloroisopropyl) phosphate (DF of 30 percent), diethoxynonylphenol (DF of 18 percent) and carbaryl (18 percent). Of the 234 samples collected, 149 had detections of at least one EDC (DF of 64 percent). The number of individual EDCs detected per sample ranged from zero to eight.

Among 179 stream samples, 126 had at least one EDC detected (DF of 70 percent). At stream sites, the number of individual EDCs detected per sample ranged from 0 to 8, with a median of 2 EDCs detected per sample. Among 55 harbor samples, 23 had at least one EDC detected (DF of 42 percent). The number of individual EDCs detected per harbor sample ranged from 0 to 6 (table 15).

The distribution and frequency of individual EDCs detected in a sample are shown in figure 53. The frequency of individual EDC constituents detected and the number of samples with EDC detections suggested that several different EDCs were present and there was a consistent source of EDCs. Sites which had EDC detections in 10 or more samples and more than 30 individual EDCs detected included Lincoln Creek, Honey Creek and Little Menomonee River. Other sites that had EDC detections in 10 or more samples included Root River at Grange Avenue (10 of 12 samples) and Milwaukee River at Mouth (10 of 12 samples). One other site had more than 30 individual EDCs detected: Kinnickinnic River, with 36 individual EDCs detected.

Figure 53. Distribution and frequency of known and suspected endocrine-disrupting compounds (EDCs) in the Milwaukee Metropolitan Sewerage District (MMSD) planning area, Wis. Color describes the number of individual EDC constituents detected (by quartiles); size of symbol describes the number of sampling events when EDCs were detected. Site abbreviations listed in table 1.

In stream samples, there were no consistent patterns between EDC detections and flow, season, or flow and season combined. Harbor samples indicated some seasonal variability; summer samples had detection frequencies around 25 percent while spring and autumn samples had detection frequencies around 50 percent.

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